Shark-Tooth Sword Reveals Lost Species

An analysis of shark-tooth weapons from the 19th century reveals two shark species, the spot-tail and dusky, where once common in the Gilbert Island reefs in the Central Pacific. The sharks are no longer found in the area.

Ironically, the dusky shark grows to about the same size as the biggest weapon measured in the study, which is published in PLoS ONE. That 15-foot-long sword was created by Gilbert Island men and was studded with sharp shark teeth.

"There was an amazing array of weapons, from shark tooth brass knuckles to lances that were about 15 feet long," lead author Joshua Drew told Discovery News. "We don't know exactly when they were first made, but we know that when the first Western people wrote about the Gilbert Islanders in the 1840s, they remarked about their weaponry."

Drew is a conservation biologist at Columbia University. He and colleagues Christopher Philipp and Mark Westneat analyzed 122 such weapons and related items, all housed at the Field Museum of Natural History in Chicago.

High-resolution photographs of the teeth, matched with known shark data, determined that eight species were hunted for the weapons. The spot-tail and dusky sharks were part of that group, but these species have never before been reported from Gilbert Island reef waters.

The discovery suggests that these two sharks were hunted by the islanders until they were locally extinct.

Historical records explain how these sharks and the others were hunted. The process involved a strict set of procedures. First, two men would go out in a narrow outrigger canoe measuring 10 to 15 feet long.

"One would use a series of coconut shells as a rattle to lure the shark close," Drew explained. "When the shark would come to take an investigatory bite, he would thrust a stick down the shark's mouth, forcing the jaws open. At the same time, the other man would slide a rope around the tail of the shark."

At that point, the immobilized shark would be fastened to the side of the canoe, hauled ashore and then killed. Its meat was consumed, with the sharkskin later used to craft household goods. The skin and the teeth were used to construct weapons.

Records of early missionaries describe how the weapons were used in intertribal warfare.

"Two main combatants would have a duel using swords and dressed in armor made of tightly woven coconut cord and helmets of dried pufferfish," Drew said. "They would be joined by several assistants who would use the long lances to try to reach over their own combatant and attack his foe."

"These thrusts would, in turn, be parried by the other combatant's assistants," he added. "So while the two main men were fighting hand to hand, there was this sort of aerial combat overhead with the 10 to 15-foot lances." While the shark teeth could clearly do some serious damage to humans, they were not enough of a defense to prevent them from overfishing.

Julia Baum, a University of Victoria biologist, has extensively studied sharks. She told Discovery News, "Drew's creative study sheds new light on how we have impacted shark populations."

It is now hoped that attention to the important cultural connection that the Gilbert Islanders have to sharks will help to spark conservation efforts in the region.

Drew explained, "Kiribati, the country within which the Gilberts lie, is already one of the most progressive countries, and I think highlighting how their traditional culture can be tied to conservation will only help them continue to be at the head of the pack when it comes to marine conservation."

-- Five rays and sharks are receiving priority attention at this week's IUCN World Conservation Congress held in Jeju, Republic of Korea. The congress is the world's largest conservation event. One of the five sharks is the porbeagle, shown here.
Porbeagles are vulnerable globally, and are classified as critically endangered in the Northeast Atlantic. Their low reproductive capacity combined with over-fishing has led to severe population declines over several parts of its range.
"Sharks and rays have traveled the Earth for more than 400 million years," said Dr. Cristián Samper, president and CEO of the Wildlife Conservation Society and keynote speaker at the Jeju congress. "Yet, in only recent decades, many of these species have become threatened from overfishing and, in some instances, have disappeared entirely from major portions of their range."
He added, "The potential loss of one of only two groups of the world's living fishes is a crisis the world community must take decisive action to address. We are calling for governments around the world to vigorously support CITES international trade regulations and strengthen fisheries management and protection measures for shark and ray species. We cannot continue to allow the destruction of these wonders of evolution."

The oceanic whitetip shark is critically endangered in the Northwest and Central Atlantic Ocean. It's frequently sought after for its fins, used to make shark fin soup. Usually the rest of the dead or dying shark is then tossed back into the sea.
Andrew Brierley, a University of St. Andrews marine ecologist, told Discovery News that when sharks like this die off, the deaths can cause a domino effect of other ecosystem losses. Shellfish, for example, may go into decline because they are consumed more by predators that the sharks would normally prey upon.
"The trophic cascade brought about by the increasing demand for shark fin soup has not only left once economically valuable bivalve fisheries in crisis, but has precipitated an ecological and culinary bankruptcy," explained Brierley.

Scalloped hammerhead sharks are endangered all around the globe. This tropical species forms large migratory schools at certain times of the year. The aggregating behavior, distinct from that of other sharks, makes the shark particularly vulnerable to fishing.
"We estimate that many millions of sharks are killed annually through both legal and illegal, unregulated and unreported fishing for the trade in fins, the prime ingredient in shark fin soup," said Dr. Rachel Graham, director of WCS's Gulf and Caribbean Sharks and Rays Program.
"The high price for fins has caused the global shark fishery to expand far beyond what is sustainable. The need for international regulation and enforcement has never been greater."

Many rays, such as these, are also in peril. The Wildlife Conservation Society and over 35 government agencies and NGO partners at the congress additionally highlighted population loss problems associated with so-called "devil rays," which feed on planktonic crustaceans. Small schooling fishes become trapped on their specialized gill rakers.
Rays are frequently captured in target fisheries and as bycatch across much of their range. One reason is that the gill rakers are dried and exported for the Asian medicinal market.

The reef manta ray, shown here, is among the world's largest fishes. Both it and the giant manta ray can grow several feet across. They are slow growing, however, typically giving birth to only one pup every two to three years.
They are migratory and occur in small, highly fragmented populations that are sparsely distributed across the world’s tropics. Manta rays are captured in targeted fisheries and incidentally as bycatch. In addition, manta rays are used for human consumption, shark bait, and -- as for devil rays -- are increasingly sought for their gill rakers.
"The international trade in shark and ray products, including fins, meat, and other body parts, is driving shark and ray fisheries around the world, and most of these are unmanaged or only minimally managed," said Dr. John Robinson, WCS's executive vice president for Conservation and Science.
"Lack of controls on fisheries and international trade puts species at risk, but also jeopardizes sustainable fisheries, ecosystems, and food security."
The Convention on International Trade in Endangered Species of Wild Fauna and Flora will meet in Thailand in March 2013.